An optical add/drop multiplexer (OADM) is an important filtering device in a current optical network, and plays an important role in developing a high-speed, large-capacity, and transparent communications network. A silicon photonics technology is a most popular optoelectronic integration technology in the industry over the past decade. In the technology, an existing microelectronic complementary metal-oxide-semiconductor (CMOS) process line and low-cost silicon materials can be fully used, to implement a wide variety of optoelectronic functional devices, for example, an optical add/drop multiplexer implemented by using a silicon-based microring scheme or an optical add/drop multiplexer implemented by using a silicon-based arrayed waveguide grating. However, a bandwidth of the optical add/drop multiplexer in the foregoing methods is untunable.
A growing quantity of new communication services are increasing people's requirements for network bandwidth. Compared with a conventional service, a new service usually has a higher dynamic characteristic and is unpredictable, so that a physical layer of a transport network needs to be more flexible. However, the bandwidth of the optical add/drop multiplexer in a common method is untunable, and this already fails to satisfy a requirement for system flexibility.